One that might not be so obvious? The temperature. When it's too hot, it takes the plane longer to takeoff and it can't climb as well. Cooler weather brings the performance levels back up but you have to watch out for frost on the wings. The optimal flying temperatures is 15 degrees Celsius or 59 degrees Fahrenheit.

Winds also play a big factor. Planes always must take off and land into the wind. Winds perpendicular to the runway, or crosswinds, can be beyond the capabilities of the aircraft and make landing a dangerous proposition.